Often as a result of parodontal infections, a decay of bone substance occurs in the jaw area, as well as a progressive loosening and finally loss of one's affected teeth. Because of bare colla dentis and bare bifurcations (area of root division of the side teeth), the intermediary stages of such infections can lead to painful conditions. Moreover, even after successfully combating parodontal infections, it is usually not possible for affected teeth to again grow in firmly. This is because bone defects in the affected teeth are filled in by connective tissues rather than new bone. This in turn is because, upon concurrent filling of the bone defect, the connective tissue grows considerably faster than bone substance. As such, an osseous regeneration (i.e., "reattachment") rarely occurs in the case of bone defects which result from parodontal infections.
A method of guided tissue regeneration with teeth was introduced to the medical world some time ago. In the method, bone defects in teeth are artificially screened and the cavities formed by the screens are allowed to simply fill up with blood. The screens are intended to prevent the growing-in of connective tissue into the cavities so that bone regeneration can take place in the cavities formed. After removal of the screen, a re-securing of the teeth is thus achievable.
In EP-B 0 171 173 semi-permeable membranes consisting of polytetrafluorethylene (PTFE) are proposed as screen materials. Resorbable tissues for producing such screens are also described in the literature. For example, in a paper given by Dr. Carla Noppe on the occasion of the 1989 Annual Conference of the Deutsche Gesellschaft fur Paradontologie on Sep. 29 and 30, 1989 in Aachen, the practical use of semi-permeable PTFE membranes was described. It was pointed out that these membranes have an open microstructure having approximately a 10 .mu.m pore size, into which gingival fibroblasts can migrate and prevent a deep epithelium growth between filter and gingiva. In the clinical trials reported, 40 membranes of various configurations were implanted for 4 to 6 weeks. Even so, the evaluation showed that in the case of 39 operation areas, a deep epithelium growth of 2 to 4 mm did occur under the membranes and large parts of the membranes were colonized by bacteria. Moreover, although the use of such membranes and tissues allowed a certain degree of success to be achieved, their clinical application was extremely difficult. For example, the flexible tissues were secured in situ only with difficulty and moreover, the low biocompatibility of the PTFE membranes necessitated their removal from application sites after only a few weeks. Similarly, deep epithelium growths could not be completely ruled out with the tissues and membranes, and likewise a bacterial colonization could not be prevented therewith.
The concept of GTR can, of course, be applied not only to bone defects in the area of the teeth, but also to other bone defects occurring in the body.